Angiotensin-receptor blockers for prevention of atrial fibrillation--a matter of timing or target?

Life's Simple 7 Approach to Atrial Fibrillation Prevention

Atrial fibrillation (AF) is the most commonly encountered arrhythmia in clinical practice. It constitutes a major public health problem, with total related annual expenses estimated at $6.65 billion. The American Heart Association developed Life's Simple 7 (LS7) to define and monitor ideal cardiovascular health (CVH). In this review, we examine the role of individual components of LS7 to provide further insight regarding potential influence of achieving AHA's strategic goal on AF prevention. While significant advances have been made in the secondary prevention of AF, little progress has been made to prevent the first occurrence of this arrhythmia in at-risk patients. Improvement of overall cardiovascular health as defined by LS7 may substantially reduce AF risk.

Atrial fibrillation

Atrial fibrillation is the most common arrhythmia affecting patients today. Disease prevalence is increasing at an alarming rate worldwide, and is associated with often catastrophic and costly consequences, including heart failure, syncope, dementia, and stroke. Therapies including anticoagulants, anti-arrhythmic medications, devices, and non-pharmacologic procedures in the last 30 years have improved patients' functionality with the disease. Nonetheless, it remains imperative that further research into AF epidemiology, genetics, detection, and treatments continues to push forward rapidly as the worldwide population ages dramatically over the next 20 years.

Renin-angiotensin system inhibitors for prevention of recurrent atrial fibrillation: a meta-analysis

INTRODUCTION

Conflicting results exist now on the clinical utility of renin-angiotensin system (RAS) inhibitors in patients with atrial fibrillation (AF). This study aimed to elaborate the efficacy and safety of RAS blockade on preventing the relapse of AF by a meta-analysis based on randomised controlled trials (RCTs).

METHODS

We searched Medline, ISI web of science and Cochrane databases through Jan 2012. We included RCTs comparing RAS inhibition treatment vs. placebo or alternative therapy after cardioversion of persistent AF or conventional medical therapy for paroxysmal AF and reporting outcome of recurrent AF. Odds ratios (OR) were calculated using a random effects model.

RESULTS

Fifteen trials involving 3972 AF patients were included in the analysis. The pooling analysis showed that RAS inhibitors significantly reduced the recurrence of AF compared with non-RAS inhibitors (OR=0.50, 95% CI: 0.37-0.69, p<0.01), and the beneficial effect was shown consistently both in patients with paroxysmal and in those with persistent AF after cardoversion. However, administration of RAS inhibitors did not provide a greater survival advantage and a lower incidence of adverse effects than the control (OR=1.17, 95% CI, 0.65-2.10, p=0.59; OR=0.94, 95% CI: 0.65-1.35, p=0.73 respectively). In addition, clinical factors potentially affecting AF relapsing had no pronounced impacts on the above clinical outcomes.

CONCLUSIONS

Based on the currently available data, inhibition of RAS is effective, safe and well tolerated for preventing the recurrence of AF.

New approaches to stroke prevention in atrial fibrillation

OPINION STATEMENT

It is estimated that atrial fibrillation (AF) is responsible for almost 15% of all strokes. Several randomized clinical trials have demonstrated the superiority of adjusted-dose warfarin over aspirin for stroke prevention in AF patients, particularly in high-risk individuals. Current national guidelines from the American Heart Association/American Stroke Association recommend the use of adjusted-dose warfarin with an international normalized ratio goal of 2.0 to 3.0 for patients with ischemic stroke or transient ischemic attack with persistent or paroxysmal AF, and aspirin for those who cannot take oral anticoagulants. However, the use of warfarin may be challenging in some patients, and there is a need for alternative treatments. We describe alternative treatments for AF and provide an overview on emerging therapies.

Therapy with renin-angiotensin system blockers after pulmonary vein isolation in patients with atrial fibrillation: who is a responder?

AIMS

The data on anti-arrhythmic effect of renin-angiotensin-aldesteron system blockers (RASB) in patients with atrial fibrillation (AF) are controversially discussed. The goal of this analysis was to identify cohort of patients with AF and hypertension, who may have benefit from RASB therapy after pulmonary vein isolation (PVI).

METHODS

A total of 284 patients with AF and hypertension (paroxysmal AF [PAF]= 218, male = 185, age = 61 years, left ventricular ejection fraction = 60%, coronary artery disease = 42) considered for PVI were included. The patients with PAF were stratified according to time spent in AF (AF burden) within 3 months prior to admission (</> 500 hours). Further patients were divided into two groups: (1) low-burden AF; (2) high-burden AF (PAF and persistent AF). In 195 patients, RASB therapy was administered. A 7-day continuous Holter electrocardiogram was performed after discharge, every 3 months thereafter and by symptoms.

RESULTS

Preventive effect of RASB was revealed in whole group (112 out of 195 [57%] vs 36 out of 89 [40%]; P = 0.025) and was more pronounced in patients with low-burden AF (79 out of 112 [71%] receiving RASB vs 27 out of 55 [49%] being on other drugs; P = 0.013). However, efficiency of RASB failed in patients with high-burden AF (33 out of 83 on RASB [40%] vs nine out of 34 on other drugs [27%]; P = 0.328).

CONCLUSIONS

Our data suggest that RASB appears to protect against AF recurrences after PVI in patients with low-burden paroxysmal AF. These results should be tested in a prospective study.

Angiotensin II signaling up-regulates the immediate early transcription factor ATF3 in the left but not the right atrium

The atria respond to various pathological stimuli including pressure and volume overload with remodeling and dilatation. Dilatation of the left atrium is associated with atrial fibrillation. The mechanisms involved in chamber-specific hypertrophy are largely unknown. Angiotensin II is hypothesized to take part in mediating this response. ATF3 is an immediate early gene found at the receiving end of multiple stress and growth stimuli. Here we characterize ATF3 as a direct target gene for angiotensin II. ATF3 expression is regulated by angiotensin receptor-mediated signaling in vivo and in vitro at the transcriptional level. ATF3 induction is mediated by cooperation between both the AT(1A) and AT₂ receptor subtypes. While AT₂R blocker (PD123319) efficiently blocks ATF3 induction in response to angiotensin II injection, it results in an increase in blood pressure indicating that the effect of angiotensin II on ATF3 is independent of its effect on blood pressure. In contrast to adrenergic stimulation that induces ATF3 in all heart chambers, ATF3 induction in response to angiotensin II occurs primarily in the left chambers. We hypothesize that the activation of differential signaling pathways accounts for the chamber-specific induction of ATF3 expression in response to angiotensin II stimulation. Angiotensin II injection rapidly activates the EGFR-dependent pathways including ERK and PI3K-AKT in the left but not the right atrium. EGF receptor inhibitor (Gefitinib/Iressa) as well as the AKT inhibitor (Triciribine) significantly abrogates ATF3 induction by angiotensin II in the left chambers. Collectively, our data strongly place ATF3 as a unique nuclear protein target in response to angiotensin II stimulation in the atria. The spatial expression of ATF3 may add to the understanding of the signaling pathways involved in cardiac response to neuro-hormonal stimulation, and in particular to the understanding of left atrial-generated pathology such as atrial fibrillation.

Prevention of atrial fibrillation by Renin-Angiotensin system inhibition a meta-analysis

OBJECTIVES

The authors reviewed published clinical trial data on the effects of renin-angiotensin system (RAS) inhibition for the prevention of atrial fibrillation (AF), aiming to define when RAS inhibition is most effective.

BACKGROUND

Individual studies examining the effects of RAS inhibition on AF prevention have reported controversial results.

METHODS

All published randomized controlled trials reporting the effects of treatment with angiotensin-converting enzyme inhibitors or angiotensin receptor blockers in the primary or secondary prevention of AF were included.

RESULTS

A total of 23 randomized controlled trials with 87,048 patients were analyzed. In primary prevention, 6 trials in hypertension, 2 trials in myocardial infarction, and 3 trials in heart failure were included (some being post-hoc analyses of randomized controlled trials). In secondary prevention, 8 trials after cardioversion and 4 trials assessing the medical prevention of recurrence were included. Overall, RAS inhibition reduced the odds ratio for AF by 33% (p < 0.00001), but there was substantial heterogeneity among trials. In primary prevention, RAS inhibition was effective in patients with heart failure and those with hypertension and left ventricular hypertrophy but not in post-myocardial infarction patients overall. In secondary prevention, RAS inhibition was often administered in addition to antiarrhythmic drugs, including amiodarone, further reducing the odds for AF recurrence after cardioversion by 45% (p = 0.01) and in patients on medical therapy by 63% (p < 0.00001).

CONCLUSIONS

This analysis supports the concept of RAS inhibition as an emerging treatment for the primary and secondary prevention of AF but acknowledges the fact that some of the primary prevention trials were post-hoc analyses. Further areas of uncertainty include potential differences among specific RAS inhibitors and possible interactions or synergistic effects with antiarrhythmic drugs.